Magneto-resistive effect element having spacer layer including gallium oxide layer with metal element

ABSTRACT

A magneto-resistive effect (MR) element includes: first and second magnetic layers in which a relative angle formed by magnetization directions changes according to an external magnetic field; and a spacer layer positioned between the first magnetic layer and the second magnetic layer. The spacer layer includes a main spacer layer composed of gallium oxide as a primary component and containing at least one metal element selected from a group of magnesium, zinc, indium and aluminum.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magneto-resistive effect (MR) elementand particularly to a configuration of a spacer layer.

2. Description of the Related Art

Reproducing heads with high sensitivity and high output are in demand inconjunction with condensing of high recording density in hard diskdrives (HDD). As an example of this type of reproducing head, a spinvalve head has been developed. A spin valve head includes a nonmagneticmetal layer and a pair of ferromagnetic layers positioned on both sidesof the nonmagnetic metal layer in a manner of contacting the nonmagneticmetal layer. The magnetization direction of one side of theferromagnetic layers is pinned in one direction (hereinafter, this typeof layer is referred to as a magnetization pinned layer), and themagnetization direction of the other side of the ferromagnetic layersfreely rotates in response to an external magnetic field (hereinafter,this type of layer is referred to as a magnetization free layer). Whenan external magnetic field is applied, the relative angle of spinsbetween the magnetization pinned layer and the magnetization free layerchanges so that magneto-resistive change is realized. Typically, themagnetization direction of the magnetization pinned layer is pinned byutilizing exchange coupling force of an anti-ferromagnetic layer. In thepresent specification, a stack in which the above-described pair offerromagnetic layers and a spacer layer are laminated is referred to asa magneto-resistive effect element (MR element).

On the other hand, in order to realize further condensing of highrecording density, a reduction of a read gap (a space between upper andlower shield layers or a height of the MR element in a laminationdirection) is required. However, when the read gap is reduced toapproximately 20 nm, placing an anti-ferromagnetic layer within the readgap becomes difficult. Therefore, a configuration has been developed inwhich a pair of magnetization free layers is arranged on both sides ofthe spacer layer. Since no anti-ferromagnetic layer is needed with thisconfiguration, it becomes easy to realize reduction of the read gap.

In any configuration, in order to realize high recording density, it isrequired to reduce not only the read gap but also a plane area of the MRelement, i.e., a cross sectional area of the MR element on a crosssection parallel to film surfaces of layers configuring the MR element.For example, in order to realize recording density of 1 Tbits/in², it isdesirable to reduce an element size to 25 nm×25 nm or less. Especially,the size reduction of the MR element in the track width direction causesa track pitch of a recording medium to be reduced. However, as the crosssectional area of the MR element is reduced, a resistance of the MRelement is increased. When the resistance of the MR element isincreased, the deterioration in the high-frequency responsecharacteristic of the MR element and the increase in noise occur, and inturn signal to noise ratio (S/N ratio) is deteriorated. Therefore, it isimportant to suppress the increase in the resistance of the MR elementwhen an element size is reduced. To achieve this, it is important toreduce a resistance-area (RA) of the MR element; and it is desirablethat the RA is 0.3 Ωμm² or less in order to achieve the recordingdensity over 1 Tbits/in².

Accordingly, a new configuration of a spacer layer has been discussedwhich allows to realize a small RA and a large magnetoresistance ratio(hereafter, referred to as the MR ratio). The U.S. Patent ApplicationPublication No. 2008/0170336 discloses a spacer layer having a threelayer configuration in which Cu layers are arranged on both sides of aZnO layer, and a metal such as Au, Ag or the like that is less likely tobe oxidized than Zn is added to the ZnO layer. By adding the metal tothe ZnO layer, the large MR ratio can be obtained while the RA ismaintained small. With an MR element using this spacer layer, the MRratio of approximately 12-13% can be obtained when the RA is 0.3 Ωμm² orless.

Normally, there is a variation among RAs of MR elements even in onewafer. When the variation is large, the number of MR elements ormagnetic heads that can be produced from one wafer is decreased;therefore a drawback remains that a yield rate deteriorates.

It is an object of the present invention to provide an MR element inwhich a configuration of a spacer layer is improved so that a large MRratio is realized while an RA variation is suppressed.

SUMMARY OF THE INVENTION

A magneto-resistive effect (MR) element of the present inventionincludes: first and second magnetic layers in which a relative angleformed by magnetization directions changes according to an externalmagnetic field; and a spacer layer positioned between the first magneticlayer and the second magnetic layer. The spacer layer includes a mainspacer layer composed of gallium oxide as a primary component andcontaining at least one metal element selected from a group ofmagnesium, zinc, indium and aluminum.

Compared to the known spacer layer formed of a metal layer such ascopper or zinc oxide, etc., the spacer layer including the main spacerlayer composed of gallium oxide as main component can realize a large MRratio. For one example, approximately double MR ratio can be obtainedwith respect to an MR element of the conventional art in which zincoxide is used for a main spacer layer. Gallium oxide normally exists inan amorphous state where in a thin film state; however, gallium oxidehas advantages in that a wide band gap can be maintained even in theamorphous state and in that no lattice matching (matching of latticeconstants of two adjacent materials) between the spacer layer and anadjacent ferromagnetic layer is required.

On the other hand, even when gallium oxide is used for the spacer layer,a problem of an RA variation, i.e., an RA variation of MR elementsproduced from one wafer exists. It is thought that the RA variation iscaused by an internal structure variation of gallium oxide such as, forexample, oxygen deficient variation and grain boundary distributionvariation. In the present invention, the main spacer layer includes atleast one metal element that is selected from a group of magnesium,zinc, indium and aluminum. The inventors of the present invention thinkthat adding such a dissimilar metal element to gallium oxide changesatom arrangement of gallium oxide so that the uniformity of the internalstructure of gallium oxide is improved. As a result, the RA variation issuppressed and it becomes possible to increase a yield rate.

The above description, as well as other objects, features, andadvantages of the present specification will be evident by the detaileddescription that follows below with reference to attached drawingsillustrating the present specification.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a main part cross sectional view of a thin film magnetic headaccording to a first embodiment.

FIG. 2 is a side view of an MR element, as viewed from the A-A directionof FIG. 1, i.e., an air bearing surface.

FIG. 3 is a cross sectional view of an MR element according to a secondembodiment, as viewed from the same direction as FIG. 1.

FIG. 4 is a schematic view illustrating a principle of performance of athin film magnetic head according to the second embodiment.

FIG. 5 is a graph illustrating the relationship between the oxide metaladditive amount and the RA variation of a first example.

FIG. 6 is a graph illustrating the relationship between the oxide metaladditive amount and the RA variation of a second example.

FIG. 7 is a perspective view of a magnetic head slider of the presentinvention.

FIG. 8 is a perspective view of a head arm assembly of the presentinvention.

FIG. 9 is a side view of a head stack assembly of the present invention.

FIG. 10 is a plan view of a hard disk device of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A number of embodiments of an MR element according to embodiments of thepresent invention and a thin film magnetic head including the MR elementwill be explained utilizing the drawings.

(First Embodiment)

FIG. 1 illustrates a main part cross sectional view of a thin filmmagnetic head 1 according to a first embodiment. The thin film magnetichead 1 is formed above a substrate W and includes a reproducing head 2and a recording head 3. FIG. 2 is a side view of the reproducing head 2,as viewed from the A-A direction of FIG. 1, and illustrates a layerconfiguration of the reproducing head 2 on an air bearing surface S. Theair bearing surface S is a surface of the thin film magnetic head 1 thatfaces a recording medium M. First, a description will be given regardinga configuration of the reproducing head 2 with reference to FIG. 2.

The reproducing head 2 includes a spin valve type MR element 4, upperand lower shield layers 6 and 5 disposed so as to sandwich the MRelement 4 in a film surface orthogonal direction (lamination direction)P, and bias magnetic field application layers 32 disposed on both sidesin a track width direction T of the MR element 4 (sheet surfaceorthogonal direction in FIG. 1). A tip end part of the MR element 4, asillustrated in FIG. 1, is arranged on the air bearing surface S. The MRelement 4 is arranged so that a sense current S flows in a film surfaceorthogonal direction P by voltage applied between the upper shield layer6 and the lower shield layer 5. A magnetic field from the recordingmedium M positioned facing the MR element 4 changes by a rotation of therecording medium M. The magnetic field change is detected as anelectrical resistance change of a sense current S based onmagneto-resistive effect. The MR element 4 reads magnetic informationwritten in the recording medium M utilizing this principle.

Table 1 illustrates one example of a layer configuration of the MRelement 4. Table 1 describes from the lower shield layer 5 through theupper shield layer 6 from bottom to up in a lamination order.

TABLE 1 Film Thickness Layer Configuration Material (nm) Upper ShieldLayer 6 NiFe 2000 MR Protective layer 18 Ru 10.0 Element 4 MagnetizationFree Layer 17 CoFe 4.0 (Second Magnetic Layer L2) Spacer SecondNonmagnetic Cu or Zn 0.7 Layer 16 Layer 16c Main Spacer Layer 16b GaOx +0.9 Metal element First Nonmagnetic Layer Cu or Zn 0.7 16a InnerMagnetization Pinned Layer 15 CoFe 3.5 (First Magnetic Layer L1)Exchange Coupling Transmitting Ru 0.8 Layer 14 Outer MagnetizationPinned Layer 13 CoFe 3.0 Anti-Ferromagnetic Layer 12 IrMn 5.0 UnderLayer 11 Ru 2.0 Ta 1.0 Lower Shield Layer 5 NiFe 2000

The MR element 4 has a layer configuration in which the following arelaminated above the lower shield layer 5 formed with an NiFe layer inthis order: an under layer 11, an anti-ferromagnetic layer 12, an outermagnetization pinned layer 13, an exchange coupling transmitting layer14, an inner magnetization pinned layer 15 (first magnetic layer L1), aspacer layer 16, a magnetization free layer 17 (second magnetic layerL2), and a protective layer 18. The protective layer 18 is covered bythe upper shield layer 6 formed with a NiFe layer.

The under layer 11 is formed with a lamination film consisting of a Talayer and a Ru layer and is disposed in order to obtain a favorableexchange coupling between the outer magnetization pinned layer 13 andthe anti-ferromagnetic layer 12 laminated on the under layer 11. Theunder layer 11 can be also configured with a lamination film consistingof a Ta layer and a NiCr layer using NiCr as an alternative for Ru. Theouter magnetization pinned layer 13 exchange couples to theanti-ferromagnetic layer 12 composed of IrMn. The outer magnetizationpinned layer 13 exchange couples to the inner magnetization pinned layer15 with the exchange coupling transmitting layer 14 composed of Rutherebetween. As a result, the magnetization direction of the innermagnetization pinned layer 15 is firmly pinned. It is desirable that theinner magnetization pinned layer 15 is magnetized in a directionorthogonal to the air bearing surface S within a film plane. Since themagnetization directions of the inner magnetization pinned layer 15 andthe outer magnetization pinned layer 13 are mutually pinned inanti-parallel orientations, overall magnetization of these combined areais suppressed. The magnetization free layer 17 in which a magnetizationdirection changes according to an external magnetic field is disposedabove the inner magnetization pinned layer 15 in a manner of sandwichingthe spacer layer 16. The protective layer 18 is disposed to prevent eachof the laminated layers from deteriorating. The outer and innermagnetization pinned layers 13 and 15 as well as the magnetization freelayer 17 are typically composed of CoFe, but may contain Ni.

The bias magnetic field application layers 32 are disposed on both sidesin the track width direction T of the MR element 4 with an insulatinglayer 31 therebetween. The bias magnetic field application layers 32 area magnetic domain controlling film for making the magnetization freelayer 17 a single magnetic domain, and applies a bias magnetic field tothe magnetization free layer 17 in the track width direction T. Theinsulating film 31 is formed of Al₂O₃, and the bias magnetic fieldapplication layers 32 are formed of CoPt, CoCrPt or the like.

A sense current S flows in the MR element 4 in the film surfaceorthogonal direction P. The sense current S is supplied from the upperand lower shield layers 6 and 5 which also function as electrodes. Themagnetization direction of the magnetization free layer 17 is controlledin the track width direction T, i.e., in the orientation orthogonal tothe magnetization direction of the inner magnetization pinned layer 15,by the bias magnetic field from the bias magnetic field applicationlayers 32 when no external magnetic field is applied. When an externalmagnetic field from the recording medium M is applied to themagnetization free layer 17, the magnetization direction of themagnetization free layer 17 rotates by a predefined angle in thepredefined direction within the film plane according to the orientationand strength of the external magnetic field. The magnetization directionof the magnetization free layer 17 forms a relative angle with themagnetization direction of the inner magnetization pinned layer 15according to the orientation and strength of the external magneticfield, and a spin dependent scattering of conductive electrons changesaccording to the relative angle, thereby a magneto-resistive change isgenerated. The MR element 4 detects this magneto-resistive change andreads magnetic information of the recording medium M.

The position of the magnetization free layer 17 and the outer and innermagnetization pinned layers 13 and 15 may be vertically reversed withrespect to the spacer layer 16. That is to say, the magnetization freelayer 17 may be positioned closer to the substrate W than the outer andinner magnetization pinned layers 13 and 15. Specifically, the layersfrom the inner magnetization pinned layer 15 to the anti-ferromagneticlayer 12 are arranged between the protective layer 18 and the spacerlayer 16 (arranged such that the inner magnetization pinned layer 15 isat the bottommost side and the anti-ferromagnetic layer 12 is at thetop-most side), and the magnetization free layer 17 is arranged betweenthe under layer 11 and the spacer layer 16.

In the present specification, in terms of the magnetization free layer17 and the inner magnetization pinned layer 15, the layer positionedcloser to the substrate W above which the MR element 4 is formed, i.e.,beneath the spacer layer 16 as viewed in the lamination direction, isreferred to as the first magnetic layer L1, and the layer positionedfarther from the first magnetic layer L1 as viewed from the substrate W,i.e., above the spacer layer 16 as viewed in the lamination direction,is referred to as the second magnetic layer L2. In the layerconfiguration illustrated in Table 1, the inner magnetization pinnedlayer 15 is the first magnetic layer L1, and the magnetization freelayer 17 is the second magnetic layer L2, and in the layer configurationwith the reversed positional relation, the magnetization free layer 17is the first magnetic layer L1, and the inner magnetization pinned layer15 is the second magnetic layer L2.

The spacer layer 16 includes a main spacer layer 16 b composed ofgallium oxide as a primary component. A film thickness of the mainspacer layer 16 b of the example of Table 1 is 0.9 nm; however, the filmthickness can be set, for example, in a range of 0.5 nm to 1.2 nm. Themain spacer layer 16 b further includes at least one metal element thatis selected from a group of magnesium, zinc, indium and aluminum. Thesemetal elements may exist in a coupled state with oxygen (oxidationstate), and also may exist in a non-coupled state with oxygen.

The main spacer layer 16 b may contain additives other than theabove-mentioned metal elements. The additives are, for example, othermetals and metal oxides. Also, the mole fraction of gallium oxide in themain spacer layer 16 b is preferably 50% or more. The composition ofgallium oxide is expressed by the general formula GaOx where the rangeof x is 1.45≦x≦1.55. The main spacer layer 16 b is normally formed in anamorphous state. GaOx has a larger resistance value and also a largerresistance change compared to Cu used in a conventional spacer layer.Therefore, a larger MR ratio may be obtained compared to theconventional MR element in which Cu is used as the spacer layer.

The main spacer layer may contain only one metal element out of themetal elements selected from the above-mentioned group. In this case, itis desirable that a ratio of “a content of the one metal element” to “atotal content of gallium and the one metal element in the main spacerlayer 16 b” is from 1% atomic percent to 30% atomic percent. Forexample, when the main spacer layer 16 b contains only Mg out of theabove-mentioned metal elements, it is good enough that the ratio of anMg content (atomic percent) to a total content (total atomic percent) ofGa and Mg in the main spacer layer is from 1% to 30%.

The main spacer layer 16 b may contain two or more metal elements out ofthe metal elements selected from the above-mentioned group. In thiscase, it is desirable that a ratio of “a total content of the two ormore metal elements” to “a total content of gallium and the two or moremetal elements in the main spacer layer 16 b” is from 1% atomic percentto 30% atomic percent. For example, when the main spacer layer 16 bcontains only Mg and Zn out of the above-mentioned metal elements, it isnecessary that the ratio of a total content (total atomic percent) of Mgand Zn to a total content (total atomic percent) of Ga, Mg and Zn in themain spacer layer is from 1% to 30%. In this case, it is unnecessarythat a ratio of “a content of each of the metal elements” to “a totalcontent of gallium and the two or more metal elements” is from 1% atomicpercent to 30% atomic percent. This is because all magnesium, zinc,indium and aluminum have a common effect of suppressing the variation ofRA of gallium oxide. In other words, even when only one type of metalelement exists in gallium oxide or even when plural types of metalelements exist, the effect of suppressing the variation of RA of galliumoxide can be equally obtained. Therefore, in order to suppress thevariation of RA, the total content of these metal elements areimportant.

Gallium oxide is a promising material for realizing a high MR ratio.However, since gallium oxide contains oxygen, when the first and secondmagnetic layers L1 and L2 are adjacent to the main spacer layer 16 b,elements contained in the first and second magnetic layers L1 and L2such as Fe, Co, Ni and the like, and particularly Fe, have a tendencyfor oxidation. When these elements oxidize, there is a tendency for theMR ratio to fall.

Therefore, for the purpose of avoiding direct contact between the mainspacer layer 16 b and the first magnetic layer L1 in order toeffectively prevent oxidation of the first magnetic layer L1, it ispreferable that the spacer layer 16 includes a first nonmagnetic layer16 a composed of copper or at least partially oxidized copper. The firstnonmagnetic layer 16 a may be composed as well of zinc or at leastpartially oxidized zinc. Oxidation of copper or zinc may occur due tooxygen diffusion from the main spacer layer 16 b. The first nonmagneticlayer 16 a is positioned between the main spacer layer 16 b and thefirst magnetic layer L1 in contact with both.

For the same purpose, the spacer layer 16 includes a second nonmagneticlayer 16 c that is composed of zinc or at least partially oxidized zincand is positioned between the main spacer layer 16 b and the secondmagnetic layer L2 in contact with both. The second nonmagnetic layer 16c may be composed as well of copper or at least partially oxidizedcopper. Oxidation of copper or zinc may occur due to oxygen diffusionfrom the main spacer layer 16 b. From the same principle, the secondnonmagnetic layer 16 c can prevent oxidation of the second magneticlayer L2.

Referencing FIG. 1 again, the recording head 3 is disposed above thereproducing head 2 with an interelement shield layer 8 formedtherebetween by a sputtering method or the like. The recording head 3has a configuration for so-called perpendicular magnetic recording. Amagnetic pole layer for writing is composed of a main magnetic polelayer 21 and an auxiliary magnetic pole layer 22. These magnetic polelayers are formed by a frame plating method or the like. The mainmagnetic pole layer 21 is formed of FeCo and is arranged on the airbearing surface S in an orientation nearly orthogonal to the air bearingsurface S. A coil layer 23 extending over a gap layer 24 composed of aninsulating material is wound around the periphery of the main magneticpole layer 21 so that a magnetic flux is induced to the main magneticpole layer 21 by the coil layer 23. The coil layer 23 is formed by aframe plating method or the like. The magnetic flux is guided within themain magnetic pole layer 21 and is emitted from the air bearing surfaceS towards the recording medium M. The main magnetic pole layer 21 istapered not only in the film surface orthogonal direction P but also inthe track width direction T near the air bearing surface S to generate aminute and strong write magnetic field in accordance with the highrecording density.

The auxiliary magnetic pole layer 22 is a magnetic layer magneticallycoupled with the main magnetic pole layer 21. The auxiliary magneticpole layer 22 is a magnetic pole layer with a film thickness betweenapproximately 0.01 μm and approximately 0.5 μm and is formed of an alloycomposed of two or three of any of Ni, Fe, Co or the like. The auxiliarymagnetic pole layer 22 is disposed in a manner that branches from themain magnetic pole layer 21 and faces the main magnetic pole layer 21with the gap layer 24 and a coil insulating layer 25 therebetween on theair bearing surface S side. The end part of the auxiliary magnetic polelayer 22 on the air bearing surface S side forms the trailing shieldpart in which the layer cross-section is wider than other parts of theauxiliary magnetic pole layer 22. The magnetic field gradient betweenthe auxiliary magnetic pole layer 22 and the main magnetic pole layer 21becomes steeper in the vicinity of the air bearing surface S byproviding this type of auxiliary magnetic pole layer 22. As a result,the signal output jitter is reduced, and the error rate during readingcan be lowered.

(Second Embodiment)

A thin film magnetic head 1 of the present embodiment is the same as thefirst embodiment indicated in FIG. 1 with the exception of theconfiguration of the reproducing head 2. FIG. 3 and Table 2 illustrate alayer configuration of such an MR element. A reproducing head 102includes an MR element 104 in which a large number of layers arelaminated in the same manner as the first embodiment, and upper andlower shield layers 106 and 105 that are disposed so as to sandwich theMR element 104 in the film surface orthogonal direction P (laminationdirection). The upper and lower shield layers 106 and 105 are also usedas electrodes for a sense current S to cause the sense current S to flowin the film surface orthogonal direction P of the MR element 104.

With the present embodiment, a first magnetic layer L1 and a secondmagnetic layer L2 are magnetization free layers 115 and 117 in both ofwhich the magnetization direction changes according to the externalmagnetic field. A bias magnetic field application layer 132 is disposedon the backside of the MR element 104, as viewed from the air bearingsurface S, with an insulating layer 131 therebetween and applies a biasmagnetic field to the first and second magnetization free layers 115 and117 (first and second magnetic layers L1 and L2) in a directionorthogonal to the air bearing surface S. A spacer layer 116 is disposedbetween the first and second magnetization free layers 115 and 117. Afirst magnetic linkage layer 111 is disposed between the firstmagnetization free layer 115 and the lower shield layer 105, and asecond magnetic linkage layer 118 is disposed between the secondmagnetization free layer 117 and the upper shield layer 106.

TABLE 2 Film Thickness Film Configuration Material (nm) Upper SecondMain Shield Layer 106a NiFe 2000 Shield Second Anti-Ferromagnetic Layer106b IrMn 6.0 Layer 106 Second Exchange Coupling Magnetic Field CoFe 1.5Application Layer 106c NiFe 20.0 MR Second Magnetic Exchange Coupling Ru0.8 Element Linkage Layer 118 Transmitting Layer 118c 104 Gap AdjustmentLayer 118b CoFe 6.0 Exchange Coupling Ru 0.8 Transmitting Layer 118aSecond Magnetization Free Layer 117 (Second CoF 4.0 Magnetic Layer L2)Spacer Layer 116 Second Nonmagnetic Layer Cu or Zn 0.4 116c Main SpacerLayer 116b GaOx + 0.9 Metal element First Nonmagnetic Layer Cu or Zn 0.6116a First Magnetization Free Layer 115 (First Magnetic CoFe 4.0 LayerL1) First Magnetic Exchange Coupling Ru 0.8 Linkage Layer 111Transmitting Layer 111e Gap Adjustment Layer 111d CoFe 6.0 ExchangeCoupling Ru 0.8 Transmitting Layer 111c Gap Adjustment Layer 111b CoFe1.0 Exchange Coupling Ru 0.8 Transmitting Layer 111a Lower FirstExchange Coupling Magnetic Field NiFe 20.0 Shield Application Layer 105cCoFe 1.5 Layer 105 First Anti-Ferromagnetic Layer 105b IrMn 6.0 FirstMain Shield Layer 105a NiFe 2000

The lower shield layer 105 includes a first main shield layer 105 a, anda first anti-ferromagnetic layer 105 b and a first exchange couplingmagnetic field application layer 105 c laminated above the first mainshield layer 105 a. The magnetization direction of the first exchangecoupling magnetic field application layer 105 c is pinned in the trackwidth direction T (sheet surface orthogonal direction) due to ananti-ferromagnetic coupling with the first anti-ferromagnetic layer 105b. Similarly, the upper shield layer 106 includes a second main shieldlayer 106 a, and a second anti-ferromagnetic layer 106 b and a secondexchange coupling magnetic field application layer 106 c laminated belowthe second main shield layer 106 a. The magnetization direction of thesecond exchange coupling magnetic field application layer 106 c ispinned in the track width direction T due to an anti-ferromagneticcoupling with the second anti-ferromagnetic layer 106 b. The first andsecond exchange coupling magnetic field application layers 105 c and 106c are magnetized mutually in the same direction. In other embodiments,instead of disposing the first and second anti-ferromagnetic layers 105b and 106 b and the first and second exchange coupling magnetic fieldapplication layers 105 c and 106 c, the magnetization directions of thefirst and second main shield layers 105 a and 106 a may be oriented inthe same direction by being formed in a long and narrow shape in thetrack width direction T and forming a single magnetic domain using ashape anisotropic effect.

The first magnetic linkage layer 111 has a structure in which gapadjustment layers 111 b and 111 d composed of CoFe are alternated andrespectively laminated with exchange coupling transmitting layers 111 a,111 c and 111 e composed of Ru, and the exchange coupling transmittinglayers 111 a and 111 e are positioned at both side end surfaces. Thesecond magnetic linkage layer 118, in the same manner as the firstmagnetic linkage layer 111, also has a structure in which a gapadjustment layer 118 b composed of CoFe is alternated and laminated withexchange coupling transmitting layers 118 a and 118 c composed of Ru,and the exchange coupling transmitting layers 118 a and 118 c arepositioned at both side end surfaces. A pair of magnetic layers 105 cand 111 b, a pair of magnetic layers 111 b and 111 d, and a pair ofmagnetic layers 111 d and 115 that respectively sandwich the exchangecoupling transmitting layers 111 a, 111 c, and 111 e perform exchangecoupling. A pair of magnetic layers 106 c and 118 b and a pair ofmagnetic layers 118 b and 117 that respectively sandwich the exchangecoupling transmitting layers 118 a and 118 c perform exchange coupling.As illustrated in FIG. 3, the magnetization directions alternatelyreverse (no bias magnetic field is applied).

The total film thickness of the MR element 104 can be adjusted to matchthe shield gap by adjusting the film thickness of the gap adjustmentlayers 111 b, 111 d and 118 b. The smaller the shield gap is, the morebeneficial it is to realize high recording density; however, the shieldgap may also be determined according to the required film thickness ofthe bias magnetic field application layer 132. In this case, it ispreferred to adjust the total film thickness, i.e., the shield gap, ofthe MR element 104 by changing the film thickness of the gap adjustmentlayers 111 b, 111 d and 118 b.

The above-described MR element 104 performs as will be describedhereinafter. A virtual condition will be considered first in which thereis no bias magnetic field application layer 132. FIG. 4 is a schematicview illustrating the magnetizations of the first and secondmagnetization free layers 115 and 117. The magnetization directions ofthe first and second exchange coupling magnetic field application layers105 c and 106 c are transmitted to the first and second magnetizationfree layers 115 and 117 while reversed at the gap adjustment layers 111b, 111 d and 118 b with the exchange coupling transmitting layers 111 a,111 c, 111 e, 118 a and 118 c therebetween. Therefore, the firstmagnetization free layer 115 is magnetized in the track width directionT toward an orientation yl that is anti-parallel to the magnetizationdirection of the first exchange coupling magnetic field applicationlayer 105 c. The second magnetization free layer 117 is magnetized inthe track width direction T toward an orientation y2 that is the same asthe magnetization direction of the second exchange coupling magneticfield application layer 106 c.

Next, a condition will be considered in which a bias magnetic field isapplied. The bias magnetic field rotates the magnetization directions ofthe first and second magnetization free layers 115 and 117 oriented inthe track width direction T toward a direction orthogonal to the airbearing surface S. As illustrated by solid line arrows x1 and x2 of FIG.4, the magnetization directions rotate by the prescribed angle θ inmutually opposite directions from the broken line arrows y1 and y2, andideally are mutually orthogonal. This is the magnetization state of thefirst and second magnetization free layers 115 and 117 when no externalmagnetic field is applied.

When an external magnetic field is applied in this state as illustratedby the outline arrows in the drawing, the magnetization directions ofthe first and second magnetization free layers 115 and 117 rotate inmutually opposite directions according to the orientation of theexternal magnetic field. When the external magnetic field is applied inthe direction A in the drawing, the magnetization directions (the solidline arrows x1 and x2) of the first and second magnetization free layers115 and 117 rotate in the direction (a) in the drawing, and when theexternal magnetic field is applied in the direction B in the drawing,the magnetization directions of the first and second magnetization freelayers 115 and 117 rotate in the direction (b) in the drawing. In thismanner, a relative angle formed by the magnetization directions of thefirst and second magnetization free layers 115 and 117 changes accordingto the external magnetic field, and the resistance value of the sensecurrent S varies based on the magneto-resistive effect. Utilizing thisprinciple, the MR element 104 can detect the orientation and strength ofthe external magnetic field.

As described above, the MR element 104 of the present embodimentincludes: a pair of magnetization free layers 115 and 117 in which themagnetization direction changes according to the external magneticfield; and the spacer layer 116 sandwiched by the magnetization freelayers 115 and 117. The MR element 104 differs from the first embodimentwith regards to the point that the magnetization directions of the pairof magnetization free layers 115 and 117 rotate mutually according tothe external magnetic field; however, the same configuration as for thespacer layer 16 in the first embodiment can be applied to the spacerlayer 116. In other words, the spacer layer 116 includes a main spacerlayer 116 b composed of gallium oxide as a primary component. The mainspacer layer 116 b further includes at least one metal element that isselected from a group of magnesium, zinc, indium and aluminum. Thespacer layer 116 includes a first nonmagnetic layer 116 a that iscomposed of copper or at least partially oxidized copper and ispositioned between the main spacer layer 116 b and the first magneticlayer L1 in contact with both. The first nonmagnetic layer 116 a may becomposed of zinc or at least partially oxidized zinc. Similarly, thespacer layer 116 includes a second nonmagnetic layer 116 c that iscomposed of zinc or at least partially oxidized zinc and is positionedbetween the main spacer layer 116 b and the second magnetic layer L2 incontact with both. The second nonmagnetic layer 116 c may be composed ofcopper or at least partially oxidized copper.

The magnetization directions of the first and second magnetization freelayers 115 and 117 can be reversed by adjusting the total number of Rulayers and gap adjustment layers included in the first and secondmagnetic linkage layers 111 and 118. For example, when the magnetizationdirections of the upper shield layer 106 and the lower shield layer 105are anti-parallel, the magnetization direction of the firstmagnetization free layer 115 can be reversed by configuring the firstmagnetic linkage layer 111 with two Ru layers 111 a and 111 c and asingle gap adjustment layer 111 b inserted therebetween as illustratedin Table. 3. In the same manner, although not illustrated in thedrawing, a similar effect can be obtained by configuring the secondmagnetic linkage layer 118 as a five layer configuration that is thesame as the first magnetic linkage layer 111 in the configurationillustrated in Table 2.

TABLE 3 Film Thickness Film Configuration Material (nm) Upper SecondMain Shield Layer 106a NiFe 2000 Shield Second Anti-Ferromagnetic Layer106b IrMn 6.0 Layer Second Exchange Coupling Magnetic Field CoFe 1.5 106Application Layer 106c NiFe 20.0 MR Second Magnetic Exchange CouplingTransmitting Ru 0.8 Element Linkage Layer Layer 118c 104 118 GapAdjustment Layer 118b CoFe 6.0 Exchange Coupling Transmitting Ru 0.8Layer 118a Second Magnetization Free Layer 117 (Second CoFe 4.0 MagneticLayer L2) Spacer Layer 116 Second Nonmagnetic Layer 116c Cu or Zn 0.4Main Spacer Layer 116b GaOx + 0.9 Metal element First Nonmagnetic Layer116a Cu or Zn 0.6 First Magnetization Free Layer 115 (First MagneticCoFe 4.0 Layer L1) First Magnetic Exchange Coupling Transmitting Ru 0.8Linkage Layer Layer 111c 111 Gap Adjustment Layer 111b CoFe 6.0 ExchangeCoupling Transmitting Ru 0.8 Layer 111a Lower First Exchange CouplingMagnetic Field Application NiFe 20.0 Shield Layer 105c CoFe 1.5 LayerFirst Anti-Ferromagnetic Layer 105b IrMn 6.0 105 First Main Shield Layer105a NiFe 2000

FIRST EXAMPLE

A multilayer film with the layer configuration illustrated in Table 1was formed above a substrate W composed of Al₂O₃—TiC (ALTIC) by using aradio frequency (RF) sputtering device. Mg, Zn, In or Al was used as ametal element to add to a main spacer layer. In the present example,these elements were added as oxides. In the following explanation,oxides of Mg, Zn, In and Al are collectively referred to as MOx. Thefilm thickness of the main spacer layer was 0.9 nm. The main spacerlayer was formed by disposing a target composed of Ga₂O₃ and a targetcomposed of MOx in a reaction chamber and colliding argon gassimultaneously with these targets. A target composed of Ga₂O₃ to whichMOx was added may be used. Copper was used for the first nonmagneticlayer 16 a and zinc was used for the second nonmagnetic layer 16 c.After the film formation, heat treatment was performed at 250° C. forthree hours. A plane size (junction size) of the MR element was 0.2μm×0.2 μm.

In the above-described MR element, the MR ratio and the average valueand variation of RA were obtained by changing the atomic percent of Mg,Zn, In and Al. The atomic percent of Mg, Zn, In and Al were specified asa ratio of a content (atomic percent) of the respective metal element toa total content (total atomic percent) of Ga and these metal elements.In other words, oxygen was excluded from a calculation of the atomicpercent. Table 4 and FIG. 5 illustrate the results. The variation of theRA was defined as σ/N(%) when the average value of the RA of respectivesamples is N and the standard deviation is σ. As a comparative example,an MR element to which no oxide metal was added, i.e., that includes amain spacer layer composed of gallium oxide, was produced in the sameprocess. Similarly, the MR ratio and the average value and variation ofthe RA were obtained. The MR ratio of respective samples was normalizedbased on the MR ratio of the comparative example set as 1.

TABLE 4 Main Spacer Layer Metal Element RA Atomic Average RA Ga₂O₃ +Percent Normalized Value Variation Sample Mox (At %) MR Ratio (Ωμm²) (%)Comparative No MOx 0 1.00 0.19 21.7 Example added #1-1 M = Mg 1 0.980.19 11.5 #1-2 M = Mg 3 0.97 0.21 9.5 #1-3 M = Mg 5 1.05 0.21 8.2 #1-5 M= Mg 10 1.06 0.18 6.5 #1-6 M = Mg 15 1.02 0.20 6.2 #1-7 M = Mg 20 1.020.25 6.8 #1-8 M = Mg 30 0.95 0.31 9.1 #1-9 M = Mg 40 0.63 0.29 18.9 #2-1M = Zn 1 0.95 0.20 14.3 #2-2 M = Zn 3 1.05 0.23 11 #2-3 M = Zn 5 1.060.21 7.8 #2-5 M = Zn 10 1.07 0.20 8.2 #2-6 M = Zn 15 1.01 0.17 8.1 #2-7M = Zn 20 0.99 0.20 8.7 #2-8 M = Zn 30 0.95 0.26 13.5 #2-9 M = Zn 400.75 0.29 17.3 #3-1 M = In 5 0.93 0.28 9.8 #3-2 M = In 10 0.98 0.28 10.4#3-3 M = In 15 1.02 0.24 10 #3-4 M = In 30 0.89 0.28 12.9 #3-5 M = In 400.56 0.29 20.1 #4-1 M = Al 5 1.02 0.22 13.4 #4-2 M = Al 10 0.92 0.2611.2 #4-3 M = Al 15 0.99 0.23 12.2 #4-4 M = Al 30 0.90 0.28 15.4 #4-5 M= Al 40 0.63 0.32 21

Even though any oxide metal was used, with the content of metal element1% (atomic percent), the variation of the RA is largely suppressed andthe same effect is expected in a range up to at least approximately 30%.On the other hand, with an excess of 30% (atomic percent), the MR ratiotends to decrease. It is considered because, when the content is in theexcess of 30%, the added metal elements behave like impurities and spinpolarized electrons scatter. Therefore, it is desirable that the upperlimit of the content of metal element is 30% (atomic percent) and thelower limit is 1% (atomic percent). The desirable range of the averagevalue of the RA is 0.1-0.3 Ω·μm² and most of the samples are in thisrange. Mg and Zn are superior in suppressing the variation of the RA inparticular, and Mg is the best out of them. In the case of Mg, theparticularly preferable range of the content is 10-20%, and in the caseof Zn, the particularly preferable range of the content is 5-20%.

SECOND EXAMPLE

A multilayer film with a layer configuration illustrated in Table 2 wasformed above a substrate W composed of Al₂O₃—TiC (ALTIC) by using a RFsputtering device. MgO, ZnO, In₂O₃ and Al₂O₃ were used as oxide metalMOx of a main spacer layer, and the film thickness of the main spacerlayer was 0.9 nm. The main spacer layer was formed in the same processas the first example. Copper was used for a first nonmagnetic layer 116a and zinc was used for a second nonmagnetic layer 116 c. After the filmformation, heat treatment was performed at 250° C. for three hours. Aplane size (junction size) of an MR element was 0.2 μm×0.2 μm.

As in the first example, the MR ratio, and the average value andvariation of the RA were obtained by changing an atomic percent of Mg,Zn, In and Al. Table 5 and FIG. 6 illustrate the results.

TABLE 5 Main Spacer Layer Metal Element Atomic RA Average RA Ga₂O₃ +Percent Normalized Value Variation Sample Mox (At %) MR Ratio (Ωμm²) (%)#5-0 No MOx 0 1.00 0.23 26.5 added #5-1 M = Mg 5 0.99 0.21 12 #5-2 M =Mg 10 1.08 0.21 9.2 #5-3 M = Mg 15 0.96 0.20 9.9 #5-4 M = Mg 30 0.770.25 13.2 #5-5 M = Mg 40 0.58 0.30 21.6 #6-1 M = Zn 5 1.01 0.22 13 #6-2M = Zn 10 0.99 0.23 11.1 #6-3 M = Zn 15 0.94 0.21 9.5 #6-4 M = Zn 300.87 0.26 13.6 #6-5 M = Zn 40 0.74 0.27 23.3 #7-1 M = In 5 0.98 0.2615.2 #7-2 M = In 10 1.00 0.25 11.3 #7-3 M = In 15 0.99 0.26 11.1 #7-4 M= In 30 0.91 0.22 17.6 #7-5 M = In 40 0.81 0.27 24.7 #8-1 M = Al 5 1.020.23 14.9 #8-2 M = Al 10 0.90 0.20 10.9 #8-3 M = Al 15 0.96 0.23 12.3#8-4 M = Al 30 0.89 0.27 15.3 #8-5 M = Al 40 0.75 0.25 22.8

The basic tendency is the same as the first example. In other words, thevariation of the RA is largely reduced only by adding small amount ofthese metal elements, and the same effect is expected when the contentis in a range up to at least approximately 30%. There is a tendency forthe MR ratio to be reduced when the content of metal element is in theexcess of 30%. Therefore, it is desirable that the upper limit of thecontent of metal element is 30% as in the first example. Since therelationship between the content of the metal elements and the variationof the RA are extremely similar to the first example, it is consideredthat sufficient effect is provided with 1% of the content in the presentexample also. Therefore, it is possible to set the lower limit of thecontent of the metal element as 1% as in the first example.

Next, the description regarding a magnetic head slider on which the thinfilm magnetic head 1 is mounted will be given. Referring to FIG. 7, amagnetic head slider 210 has a substantially hexahedral shape, and onesurface of the six outer surfaces is the recording air bearing surface Sthat faces a hard disk. The magnetic head slider 210 is arranged in thehard disk device so as to face the hard disk, which is a disk-shapedrecording medium M that is rotatably driven. When the hard disk rotatesin the z-direction of FIG. 8, air flow passing between the hard disk andthe magnetic head slider 210 generates a downward lifting force in they-direction to the magnetic head slider 210. The magnetic head slider210 flies above the surface of the hard disk due to the lifting force.In the vicinity of the edge part of the magnetic head slider 210 (edgepart in bottom left of FIG. 8) on the air flow exit side, the thin filmmagnetic head 1 is formed.

Referring to FIG. 8, a head gimbal assembly 220 includes the magnetichead slider 210 and a suspension 221 elastically supporting the magnetichead slider 210. The suspension 221 includes a load beam 222, a flexure223 and a base plate 224. The load beam 222 is formed of stainless steelin a plate spring shape. The flexure 223 is arranged in one edge part ofthe load beam 222. The base plate 224 is arranged in the other edge partof the load beam 222. The magnetic head slider 210 is joined to theflexure 223 to give the magnetic head slider 210 suitable flexibility.At the part of the flexure 223 to which the magnetic head slider 210 isattached, a gimbal part is disposed to maintain the magnetic head slider210 in an appropriate orientation.

An assembly in which the head gimbal assembly 220 is mounted to an arm230 is referred to as a head arm assembly 221. The arm 230 moves themagnetic head slider 210 in a track crossing direction x of a hard disk262. One edge of the arm 230 is attached to the base plate 224. To theother edge of the arm 230, a coil 231 that forms one part of a voicecoil motor is attached. A bearing part 233 is disposed in the middlepart of the arm 230. The arm 230 is rotatably supported by a shaft 234attached to the bearing part 233. The arm 230 and the voice coil motorfor driving the arm 230 configure an actuator.

Next, referring to FIGS. 9 and 10, the description will be given withregard to a head stack assembly in which the above-described magnetichead slider is integrated, and the hard disk device. The head stackassembly is an assembly in which the head gimbal assembly 220 isattached to each arm of a carriage including a plurality of the arms.FIG. 9 is a side view of the head stack assembly, and FIG. 10 is a planview of the hard disk device. The head stack assembly 250 includes acarriage 251 including a plurality of arms 230. On each of the arms 230,the head gimbal assembly 220 is attached so that the head gimbalassemblies 220 align mutually at an interval in the vertical direction.On the side of the carriage 251, which is the backside to the arm 230, acoil 253 is mounted to be a part of the voice coil motor. The voice coilmotor includes permanent magnets 263 arranged so as to sandwich the coil253 and to face each other.

Referring to FIG. 10, the head stack assembly 250 is integrated in thehard disk device. The hard disk device includes multiple hard disks 262attached to a spindle motor 261. For each of the hard disks 262, twomagnetic head sliders 210 are arranged in a manner of sandwiching thehard disk 262 and facing each other. The head stack assembly 250 exceptfor the magnetic head slider 210 and the actuator position the magnetichead slider 210 with respect to the hard disk 262 in correspondence witha positioning device as well as supports the magnetic head slider 210.The magnetic head slider 210 is moved in the track crossing direction ofthe hard disk 262 by the actuator, and is positioned with respect to thehard disk 262. The thin film magnetic head 11 included in the magnetichead slider 210 records information to the hard disk 262 with therecording head 3, and reproduces information recorded on the hard disk262 with the reproducing heads 2 and 102.

While preferred embodiments of the present invention have been shown anddescribed in detail, and it is to be understood that variety of changesand modifications may be made without departing from the spirit of scopeof the following claims or its scope.

What claimed is:
 1. A magneto-resistive effect (MR) element, comprising: first and second magnetic layers in which a relative angle formed by magnetization directions changes according to an external magnetic field; a spacer layer positioned between the first magnetic layer and the second magnetic layer, the spacer layer includes a main spacer layer composed of gallium oxide as a primary component and containing at least one metal element selected from a group of magnesium, zinc, indium and aluminum. a first nonmagnetic layer positioned between the main spacer layer and the first magnetic layer and composed of copper or at least partially oxidized copper, or zinc or at least partially oxidized zinc; and a second nonmagnetic layer positioned between the main spacer layer and the second magnetic layer and composed of copper or at least partially oxidized copper, or zinc or at least partially oxidized zinc.
 2. The magneto-resistive effect (MR) element according to claim 1, wherein the main spacer layer includes one of the metal elements selected from the group, and a ratio of a content of the one of the metal elements to a total content of gallium and the one of the metal elements in the main spacer layer is from 1% atomic percent to 30% atomic percent.
 3. The magneto-resistive effect (MR) according to claim 1, wherein the main spacer layer includes two or more of the metal elements selected from the group, and a ratio of a total content of the two or more of the metal elements to a total content of gallium and the two or more of the metal elements in the main spacer layer is from 1% atomic percent to 30% atomic percent.
 4. The magneto-resistive effect (MR) element according to claim 1, wherein either the first magnetic layer or the second magnetic layer is a magnetization free layer in which a magnetization direction changes according to the external magnetic field, and the other is a magnetization pinned layer in which a magnetization direction is pinned according to the external magnetic field, and the magnetic head further comprises a pair of bias magnetic field application layers that is disposed on both sides of the MR element in a track width direction and that applies a bias magnetic field in the track width direction to the magnetization free layer.
 5. The magneto-resistive effect (MR) element according to claim 1, wherein both the first magnetic layer and the second magnetic layer are magnetization free layers in which magnetization directions change according to the external magnetic field, and the magnetic head further comprises a bias magnetic field application layer that is disposed on a back surface side of the MR element as viewed from an air bearing surface and that applies a bias magnetic field in a direction orthogonal to the air bearing surface to the first and second magnetic layers.
 6. A magnetic head slider in a hexahedral shape comprising: an air bearing surface; and the MR element according to claim 1 disposed on the air bearing surface.
 7. A head gimbal assembly comprising: the magnetic head slider according to claim 6; and a suspension elastically supporting the magnetic head slider.
 8. A hard disk drive device comprising: a hard disk; the magnetic head slider according to claim 6; and a positioning device that positions the magnetic head slider with respect to the hard disk. 